Aphasia is a communication disorder that affects 80,000 people per year and estimates suggest that VHA outpatient clinics see 2000 new cases of aphasia each year. As in other healthcare disciplines, speech-language pathologists are increasingly called upon to document the impact of their interventions with respect to functioning, activities, and social participation. One response has been the development of patient-reported outcome (PRO) measures for a range of health conditions. The goal of this proposal is to enhance the validity and clinically utility o a new PRO measure for veterans with aphasia, the Aphasia Communication Outcome Measure (ACOM). This tool will assist clinicians and researchers in responding to growing mandates to focus on patients' experiences in improving the quality and efficiency of care. In the initial fiel trial of the ACOM, a plausible and clinically useful measurement model for the ACOM was identified; its covariance-based reliability was estimated to be high; and it was found to correlat positively with other measures of communicative functioning and language performance as predicted. The next steps in maximizing the ACOM's clinical utility are to assess its sensitivity t change over time, the stability of its measurement model, and its relationships to other relevant variables. First, the responsiveness of the ACOM to treatment-related change will be assessed in collaboration with 3 independent VA RR&D-funded treatment studies by collecting pre- and post-treatment data from at least 60 participants to test whether the ACOM demonstrates reliable positive change in response to treatment. Estimates of its responsiveness and minimally important difference scores will be obtained. Second, confirmatory tests of the ACOM measurement model and the stability of its item parameters will be conducted in a sample of 300 participants with aphasia in order to verify that its internal structure applies to the intende population. Test-retest stability of score estimates in the absence of treatment will also be assessed this sample. Third, in a sub-sample of 240 participants with aphasia, correlations among the ACOM, a performance-based measure of language impairment, and concurrent PRO measures of communication, cognitive, and physical functioning will be estimated to evaluate convergence with more related constructs and discriminant evidence for less related constructs. We will also use data collected from this subsample to assess the unique contribution of ACOM for predicting communication-related well-being over and above a measure of language impairment and a PRO measure of general negative mood. The outcomes of this proposal will include (1) estimates of the responsiveness of the ACOM to treatment and benchmarks for interpretation, (2) evidence supporting the validity of the ACOM's internal structure and the stability of its item parameters, and (2) evidence supporting claims that the ACOM in fact measures the underlying construct of patient-reported communicative functioning.